Numerous processes use radial flow reactors to effect the contacting of particulate matter with a gaseous stream. These processes include hydrocarbon conversion, adsorption, and exhaust gas treatment. These reactors contain a vertically extending annular bed of particles through which the gases flow in an inward or outward direction. The annular bed is formed by an outer screen element located along the outer diameter of the particle bed and an inner screen element located along the inner diameter of the particle bed. The outer screen element often consists of a series shallow profile closed conduits having an oblong cross-section that circles the outside of the particle bed and borders the inside of the particle containing vessel. The outer screen element can also be provided by a cylindrical screen or basket structure that retains particles in its interior and provides a gas distribution space about its exterior. This invention does not apply to such cylindrical screen or basket arrangements. One familiar geometry for the oblong conduits has a scallop shaped cross-section and such conduits are hereinafter referred to as scallops. Scallops are preferred in many applications due to lower cost and simplicity of design as compared to many continuous screen designs. The conduits have the oblong or scallop shape so that the backs of the conduits will fit closely against the wall vessel thereby minimizing the volume between the back of the conduit and the vessel and maximizing the central bed volume of the vessel.
Unfortunately, the space between the vessel wall and conduits or scallops cannot be completely eliminated and such reactors in some applications suffer from problems of support crushing and/or coke accumulation between conduits or scallops and between the back of the scallop or conduit and the vessel wall. Both of these problems stem in part from the closed structure of the scallop and its placement against the wall of the contacting vessel which still leaves the small space between the back of the scallop or vessel and the reactor wall. Crushing of scallop supports occurs when the scallops are supported by the vessel wall and hot vapor first enters or leaves the vessel thereby quickly heating the relatively thin scallops which expand rapidly while the vessel wall, which is not in direct contact with the vapor, expands at a much slower rate thereby crushing the scallop supports. Since direct vapor flow does not reach the space between the back of the scallops and vessel wall, catalyst between scallops also remains relatively inactive since the vapor tends to flow primarily out of the front face of the scallop. As a result, these spaces remain inactive or dead so that solid deposits can accumulate behind or between the scallops. These deposits include reaction products and reaction by-products. One such deposit is coke that commonly forms in reforming reactions. In extreme cases, coke deposits have pushed scallops away from the wall of reforming reactors.
It is an object of this invention to provide a distribution/collection conduit for a particle contacting vessel that will diminish or eliminate the above mentioned problems.
It is also an object of this invention to provide a fluid particle contacting process that will diminish or eliminate the above-mentioned problems.
More specifically, it is an object of this invention to alleviate or prevent damage to scallops and scallop supports in reforming reactors.
As a further object, this invention seeks to improve flow distribution in a fluid particle contacting vessel.